During arc welding, an arc is produced between a wire electrode and the workpiece to be welded. The workpiece is thus heated by the arc and the wire electrode is melted. The arc can be produced by application of a direct or alternating current. The electric arc between the wire electrode melting as an additional material and the workpiece is used as a heat source for welding purposes. The high temperature of the arc melts the material at the weld site. Welding current transformers with or without a welding rectifier, welding converter or welding inverter can be used as welding current sources. Depending on the application and electrode type, direct current or alternating current is supplied to the melting wire electrode. The melting of the wire electrode is compensated for by continuous replenishment so that the arc length remains constant.
In the case of gas-shielded metal-arc welding, GSMAW, a protective gas additionally protects the weld site against the effects of the surrounding atmospheric air. In particular, such a protective gas can prevent oxidation of the weld site. In gas-shielded metal-arc welding, GSMAW, a melting wire electrode is used as an additional material. In gas-shielded metal-arc welding a differentiation is made according to the type of gas used between a metal active gas, MAG, and metal inert gas, MIG, welding process. The protective gas protects the liquid metal below the arc from oxidation, whereby the weld seam on the workpiece would be weakened.
During metal active gas welding, MAG, the welding process is carried out either with pure carbon dioxide or with a mixed gas of argon and small proportions of carbon monoxide or oxygen. During metal inert gas welding, MIG, argon is used as a noble gas, or more rarely even the noble gas helium is used. During gas-shielded metal-arc welding, GSMAW, i.e. with the MAG method or MIG method, an arc is produced between the wire electrode or the welding wire and the workpiece.
In conventional welding apparatuses the wire electrode or the welding wire is supplied to the workpiece via a wire feed device. The resistance heating and arc heating melts the supplied welding wire. The material melted at the wire electrode passes as a droplet onto the workpiece and at that location melts to form the weld seam. The protective gas flows out of a nozzle surrounding the wire electrode or the welding wire and thus protects the arc and the melt bath against surrounding atmospheric air.
In conventional welding apparatuses, compressed air can additionally be supplied via a compressed air line from a source of compressed air to the welding torch of the welding apparatus. With the aid of this compressed air, welding residues produced during welding can be blown away or the weld site can be cleaned with the aid of compressed air.
In conventional welding apparatuses it is necessary, under certain operating conditions, to axially fix the supplied welding wire, which is unwound from a supply spool and is conventionally conveyed via a guide hose, with respect to its guide. The welding wire is in that case held by a welding wire clamping device so that the torch-side end of the welding wire cannot be axially displaced with respect to the welding torch.
In conventional welding apparatuses such an actuator, e.g. the welding wire clamping device, is actuated by a separate motor or drive device. In this drive device for the actuator, power in the form of electric current is generally supplied via current supply lines. In the case of conventional welding apparatuses, the complexity thereof is increased by the provision of drive devices for internal actuators, e.g. a welding wire clamping device. Furthermore, in conventional welding apparatuses it is not possible to attach external actuators, which are provided e.g. for operating a tool, to the welding apparatus.